The prior art and the work process are: AE (i.e. “Automatic Exposure”) algorithm in the 3A algorithm, and current AE algorithm implements changes of brightness by driving aperture, shutter and gain so as to eventually achieve the optimal brightness where the brightness can be identified by human eyes for different scenes.
The control principle of the AE algorithm is: setting a reference brightness A, changing a brightness cY in a real-time scene by controlling aperture, exposure time and gain (these three are referred to as module variables hereafter) and acquiring the brightness cY which is marked as B in real time, and ending the AE control when B value equals to A value; wherein the relationship between the aperture and cY is that the bigger the aperture, the greater cY, and the smaller the aperture, the smaller cY; similarly, the greater the exposure time or the gain, the greater cY, and the smaller the exposure time or the gain, the smaller cY; and based on the relationships between the module variables and cY, AE implements controlling module variables in different scenes so that image variables reach the optimal brightness which is identified by human eyes.
Nevertheless, current AE algorithm exists some deficiencies on ensuring optimal shutter and optimal depth of field (optimal aperture) when ensuring optimal brightness, and following problems would appear:
Problem 1. Image jittering under a high magnification; Problem 2. Monitored vehicle's tailing in road scene; Problem 3. Image blurring caused by too small depth of field in evening scene, etc.